Motor

ABSTRACT

A motor includes a stator, a rotor, a top magnetic structure, and a bottom magnetic structure. The stator is disposed in a frame. The rotor is also disposed in the frame, corresponding to the stator. The rotor includes a shaft extending axially from the rotor. The bottom magnetic structure is at the bottom of the frame. The top magnetic structure is on the top of the frame. The top and bottom magnetic structures are opposite to each other in an axial direction. Magnetic attraction generated between the first magnetic structure and the shaft, and the second magnetic structure and the shaft positions the shaft therebetween such that the first magnetic structure, the second magnetic structure, and the shaft are coaxially aligned.

CROSS REFERENCE TO RELATED APPLICATIONS

This Non-provisional application is a Continuation Application claimingthe benefit of U.S. Non-provisional Application No. 10/878,114 filed onJun. 29, 2004, and for which priority is claimed under 35 U.S.C. § 120;and this application claims priority of Application No. 092122447 filedin Taiwan Aug. 15, 2003 under 35 U.S.C. § 119; the entire contents ofall are hereby incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a motor, and in particular to a highpower motor not utilizing bearings.

2. Description of the Related Art

A conventional motor comprises a shaft, a rotor, and a bearing. Therotor is disposed on the shaft and supported by the bearing, enablingthe rotor to rotate smoothly.

Mechanical components reducing friction and bearing loads in rotary andlinear drives include ball and roller bearings, sleeve bushings, dynamicbearings, magnetic bearings, and other configurations.

A ball bearing comprises an outer ring, an inner ring, and a pluralityof metal balls disposed therebetween. The ball bearing is actuated byrolling of the metal balls. Only one contact point between the metalballs and the inner or outer ring allows easy acceleration of the motor.The structure of the ball bearing, however, is weak and susceptible toimpact. In addition, when the motor with the ball bearing is operated,the balls roll at high speeds, resulting in producing high noise level.The structural interface between the balls and the inner and outer ringsrequires a high degree of accuracy, thus increasing manufacturing costs.

A sleeve bearing is formed by mixing and sintering bronze powder, ironpowder, nickel powder, lead powder and other metal powders. Lubricant isapplied into the pores of the bearing. The sleeve bearing, when disposedin a motor, is fastened in the central position of the stator. The shaftof the rotor is disposed in the bearing such that a gap is maintainedbetween the bearing and the shaft. When the motor is operated, thelubricant exudes from the bearing such that the rotor rotates in thelubricant. This type of bearing can sustain higher impact than the ballbearing, and manufacturing costs are also reduced. In a motor utilizingthe sleeve bearing, however, the lubricant evaporates into gaseous phaseas the bearing is operated over long periods. As a result, the shaftdirectly contacts the bearing such that friction is producedtherebetween. Furthermore, nitrides can possibly form at the ends of thebearing, causing damage and increasing noise level. In addition, dust inthe air may be drawn into the center of the motor during operation,contaminating the lubricant surrounding the bearing, increasing noiselevel and occluding moving parts. Furthermore, since the gap between thebearing and the shaft is small, the efficiency in starting the motor isreduced.

A dynamic bearing is a variation of the sleeve bearing. This type ofbearing comprises an inner wall with two annular arrays of V-shapedgrooves formed therein. During operation, air. and lubricant areimpelled toward the pointed ends of the grooves forming two oil-gascushions to support the shaft. In a motor with this type of bearing, theoil-gas cushion, formed at the pointed end of the V-shaped groove, isunable to be dispersed or evaporated. Formation of the groove on theinner side of the dynamic bearing, however, requires precisemanufacturing. Furthermore, the gap between the shaft and the bearingmust be accurately maintained. Thus, the manufacturing cost is higherthan other types of bearings. Moreover, when the motor operates at lowspeed, the oil-gas cushion is not formed. Thus, the dynamic effect isnot achieved at low speeds, such that performance of the dynamic bearingis substantially the same as a sleeve bearing.

A magnetic bearing has a plurality of N-S (north-south) magnetic polesformed on the shaft. The bearing corresponding to the shaft has the sameN-S poles formed thereon. During operation, repellant force suspends theshaft in the bearing. Because there is no direct contact between theshaft and the bearing, neither noise nor friction is generatedtherebetween. The magnetic bearing, however, must be designed with a gapof about 0.2 mm between the shaft and the bearing, such that balancedforce toward the center point is generated by each portion of thebearing surrounding the shaft. However, if the position of the shaft isoffset by external force or driving force during operation, theimbalance can cause shaft contact with the bearing. This increasesnoise, shortens lifetime, and can even interrupt normal operation of themotor.

Furthermore, since the magnetic bearing is based on magnetic balance,there are occasions that the motor cannot be smoothly started. Thus, themagnetic bearing is still in an experimental stage, as yet unable to bemass produced.

SUMMARY

Accordingly, an object of the present invention is to provide a motorminimizing problems associated with bearings.

The present invention provides a motor comprising a stator, a rotor, atop magnetic structure, and a bottom magnetic structure. The stator andthe rotor are disposed correspondingly in a frame. The rotor comprises ashaft, extending axially from the rotor. The shaft does not contact thestator or the frame. The bottom magnetic structure is disposed in thebottom of the frame. The top magnetic structure is disposed in the topof the frame. The magnetic structures are disposed opposite to eachother in an axial direction. Magnetic attraction generated between themagnetic structures positions the shaft therebetween such that the firstmagnetic structure, the second magnetic structure, and the shaft arecoaxially aligned.

According to the motor of the present invention, the shaft attracts orcontacts the top magnetic structure, the bottom magnetic structure, orthe magnetic structures. Furthermore, the motor includes at least onewear-resistant structure, disposed between the shaft and the bottommagnetic structure, the shaft and the top magnetic structure, or theshaft, the top, and the bottom magnetic structures. The shaft contactsthe wear-resistant structure at a contact point.

Accordingly, the motor further includes a magnetic structure encirclingthe rotor and a permeable structure encircling the stator and disposedcorresponding to the magnetic structure encircling the rotor. Themagnetic structure encircling the rotor includes a magnetic centralplane, positioned slightly higher or lower than, or level with themagnetic central plane of the permeable structure in an axial direction.

Furthermore, in the present invention, when the stator is covered by therotor, the shaft extends through the central opening of the stator, anda protective structure is formed on a sidewall of the opening withoutdirectly contacting the shaft.

In addition, the end surface of the shaft is selected from the groupconsisting of flat, curved, pointed, concave, convex, and combinationsthereof, as is the end portion of the top or bottom magnetic structurefacing the end surface of the shaft correspondingly. Moreover, the shapeof an end of the wear-resistant structure facing the axle shaft alsocorresponds to that of the shaft point.

In the motor of the invention, a plurality of blades surround theperiphery of the rotor. The blades are centrifugal, planar, or axial.The frame comprises an upper cover and a lower cover, connected byfitting, engaging, gluing, locking, connecting via a cushion device, orcombinations thereof and corresponding to each other.

Accordingly, the upper and lower magnetic structures and the shaft arecoaxial.

The present invention also provides a motor, applicable in a fanassembly, comprising a stator, a rotor, a plurality of blades, and atleast one magnetic structure. The stator is disposed on a basecomprising at least one permeable structure. The rotor comprises ashaft. The shaft extends axially from the rotor. The magnetic structureencircles the rotor, corresponding to the permeable structure. Theblades surround the periphery of the rotor, and the magnetic structureis fastened on the base via magnetic attraction to position the shaft.The magnetic structure contacts the shaft at a contact point. Themagnetic central plane of the rotor is positioned substantially higherthan the magnetic central plane of the stator.

As a result, the rotor shaft contacts the stator at a contact point.During operation, buoyant force or lifting force is generated by airflowwithout making direct contact, thereby greatly reducing noise from themotor and increasing the lifetime.

Moreover, the motor of the present invention is operated via magneticattraction of the shaft and buoyant force is generated during rotationby airflow, and thus, noise from the motor is reduced and lifetime isincreased. The motor with a conventional bearing is replaced by themotor of the invention to eliminate components and reduce assembly coststhus minimizing manufacturing cost.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a schematic diagram of a motor according to a first embodimentof the present invention;

FIG. 2 is a schematic diagram of a motor according to a secondembodiment of the present invention;

FIGS. 3A to 3D are local enlarged schematic diagrams of a shaft of themotor according to the present invention;

FIG. 4 is a schematic diagram of a motor according to a third embodimentof the present invention;

FIG. 5 is a schematic diagram of a motor according to a fourthembodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a motor according to a first embodimentof the present invention. The motor 100 comprises a frame 102, a stator104, a rotor 106, and magnetic structures 108 and 110. A shaft 116extends axially from the rotor 106. The shaft 116 and the magneticstructures 108 and 110 are aligned coaxially. In the motor 100, themagnetic attraction is generated between the magnetic structures 108 and110 and the shaft 116.

The frame 102 protects the motor 100 and internal elements thereof fromexternal force. The frame 102 is either integrally formed or comprisesan upper and a lower cover 102 a and 102 b. The frame 102 may also beformed by a plurality of divided portions (not shown). The covers 102 aand 120 b are connected by fitting, engaging, gluing, locking, orconnecting via a cushion device. Furthermore, the upper and lower covers102 a and 102 b are correspondingly engaged, for example, engaged by ahook, as shown in FIG. 1.

The stator 104 is disposed in the frame 102 to produce induced currentor provide driving force for the rotor 106. The stator 104 comprises aprinted circuit board (not shown), a stator fixing base 112, and atleast a permeable structure 114. The stator 104 does not contact theshaft 116 described later. The permeable structure 114 surrounds thebase 112 and comprises a magnetic central plane P1. The permeablestructure 114 can be a silicon steel plate or an electromagnet.

The rotor 106 is movably disposed in the frame 102, corresponding to thestator 104. The rotor 106 comprises the shaft 116, rotor 132, at leastone magnetic structure 118, a permeable cover 120. The shaft 116comprises a flat, curved, pointed, concave, or convex end surface.

The magnetic structure 118 comprises a magnetic central plane P2. Themagnetic structure 118 corresponds to the permeable structure 114. Themagnetic central plane P1 is positioned higher, level with, or lowerthan the magnetic central plane P2 in the axial direction of the shaft.The magnetic structure 118 is a permanent magnet or a plastic magnet.

In addition, the rotor 106 further comprises a plurality of blades forproducing airflow around the motor 100 during rotation of the rotor 106.The type of the blades 122 can be centrifugal, planar, or axial.

The magnetic structures 108 and 110 are disposed on the bottom and thetop of the frame 102, respectively, corresponding to a respective end ofthe shaft. The magnetic structures 108 and 110 are permanent magnets,plastic magnets, or electromagnets. The two structures 108 and 110 canbe connected and fastened on the frame 102 by gluing, fitting, engaging,or contacting. The surfaces of the magnetic structures 108 and 110facing each other have opposite polarities therebetween. The surface ofthe magnetic structures 108 and 110 facing the shaft 116 and the endsurface of the shaft 116 are curved, where the magnetic structures 108and 110 contact the shaft 116 at a contact point. The surface shape canbe flat, curved, pointed, concave, or convex.

The magnetic structures 108 and 110 and the shaft 116 are coaxiallymaintained by the magnetic attraction therebetween such that the shaft116 is positioned between the magnetic structures 108 and 110. When themotor 100 is idle, the shaft 116 also can only contact the magneticstructure 108 at a contact point, without contacting other elements.

Furthermore, the shaft 116 also may only contact the other magneticstructure 110 at a contact point such that the rotor 106 is suspended inthe frame 102.

Moreover, the shaft 116 can also contact the magnetic structures 108 and110 at a contact point simultaneously.

To further increase the lifetime of the motor 100, wear-resistantstructures 124 and 126 may be additionally disposed between the shaft116 and the magnetic structures 108 and 110. In this case, the shaft 116only contacts the wear-resistant structures 124 and/or 126 at a contactpoint. The wear-resistant structures 124 and 126 are fixed onto themagnetic structures 108 and 110 respectively. The wear-resistantstructures 124 and 126 can be formed on the magnetic structures 108 and110 simultaneously or at the intersection between the shaft 116 and themagnetic structures. Put simply, the wear-resistant structure 124 isformed on the magnetic structure 108, and the wear-resistant structure126 is formed on the magnetic structure 110. The wear-resistantstructures 124 and 126 are formed thereon by gluing, engaging, fitting,contacting, or combinations thereof. The wear-resistant structures 124and 126 can either directly contact or not contact the magneticstructures 108 and/or 110 and are coaxially aligned with the magneticstructures 108 and 110.

Furthermore, to prevent damage on the motor 100 due to impact betweenthe shaft 116 and the stator fixing base 112 during transport, aprotective structure 128 can be disposed on an opening 130 at an innerside of the stator fixing base 112. The protective structure 128 doesnot contact the shaft 116. The material of the protective structure 128can be selected from the group consisting of plastic, flexible material,vibration absorbing material, and combinations thereof.

FIG. 2 is a schematic diagram of a motor 200 according to a secondembodiment of the present invention, from which elements common to thefirst embodiment are omitted. The difference is that only one magneticstructure 202 is used to attract the shaft 116 of the rotor 106. Themagnetic central plane P2 of the magnetic structure 118 is higher thanthe magnetic central plane P1 of the permeable structure 114 in an axialdirection with respect to a base 208.

In this embodiment, the magnetic structure 202 is entirely made of amagnetic material, or formed by a wear-resistant structure 206 and amagnetic body 204. Moreover, the surface between the magnetic structure202 and the shaft 116 or the surface between the wear-resistantstructure 206 and the shaft 116 is curved with a contact pointtherebetween. The surface of the magnetic structure 202 and/or thewear-resistant structure 206 is curved, pointed, concave, convex, orcombinations thereof. The relationship between the shaft 116 and themagnetic structure 202 is the same as the above description.

When an end of a shaft 116 a or 116 b has a pointed shape, the surfaceof the magnetic structure 202 a or 202 b is curved or shaped in concavecorresponding to the end of the shaft 116 a or 116 b as shown in FIG. 3Aor 3B.

Furthermore, as shown in FIG. 3C, a curved end of a shaft 116 c iscorresponding to a convex end of the protruding magnetic structure 202c. Similarly, as shown in FIG. 3D, the shaft 116 d has a differentlyshaped depression corresponding to the pointed magnetic structure 202 d.

FIG. 4 is a schematic diagram of a motor 300 according to a thirdembodiment of the present invention, from which elements common to saidembodiments are omitted. The difference is that a magnetic structure 304is disposed on the top of the stator fixing base 112, and a magneticstructure 302 is formed on the rotor hub 132. The magnetic structures302 and 304 are attracted to each other without making contact. Themagnetic structure 304 does not contact the permeable structure 114 andis positioned higher than the permeable structure 114 in an axialdirection. The magnetic structure 302 is a circular, fan-shaped,block-shaped, or rectangular structure. The shape and position of themagnetic structure 302 correspond to those of the magnetic structure304.

Furthermore, the magnetic structure 304 and the stator fixing base 112are connected by gluing, fitting, engaging, contacting, or combinationsthereof. The magnetic structure 302 and the rotor hub 132 are alsoconnected by gluing, fitting, engaging, contacting, or combinationsthereof.

FIG. 5 is a schematic diagram of a motor 400 according to a fourthembodiment of the present invention, from which elements common to saidembodiments are omitted. The difference is that there is only onemagnetic structure 402 formed on an upper cover 102 a of the frame 102.The magnetic central plane P2 of the magnetic structure 118 is lowerthan the magnetic central plane PI of the permeable structure 114 in anaxial direction. Moreover, a wear-resistant structure 408 is disposed ata lower cover 102 b.

In this embodiment, the magnetic structure 402 is entirely made of amagnetic material, or formed by a wear-resistant structure 406 and amagnetic body 404. Moreover, the surface between the magnetic structure402 and the shaft 116, the surface between the wear-resistant structure406 and the shaft 116, and/or the surface between the wear-resistantstructure 408 and the shaft 116 is a curved surface with a contact pointtherebetween. The surface shape of the magnetic structure 402 and/or thewear-resistant structures 406, 408 is curved, pointed, concave, convex,or combinations thereof.

The motor described above is applied in an axial flow fan. The presentinvention, however, is not limited to the disclosed fan. The motor isalso applicable in other fans such as frameless, centrifugal,outer-rotor, or inner-rotor fan.

In the above embodiments, the shaft of the rotor has only one point ofcontact with the stator or no contact therebetween when buoyant airflowforce is generated during rotation. Thus, the noise level of the motoris greatly reduced and lifetime is increased.

Furthermore, the motor of the present invention generates buoyant forceby magnetic attraction from the shaft during operation such that theshaft does not contact other elements thus reducing noise and increasingthe lifetime of the motor.

The motor of the present invention does not require the conventionalbearing, thus reducing the number of elements in the motor, therebyminimizing the manufacturing cost.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A fan assembly comprising: a stator disposed in a frame; a rotor disposed in the frame and corresponding to the stator and comprising a shaft without any sleeve, hydrodynamic, ceramic or ball supports; at least one first magnetic structure disposed at a bottom of the frame; and at least one second magnetic structure disposed in the frame; wherein magnetic interaction generated between the first magnetic structure and the shaft, and the second magnetic structure and the shaft positions the shaft therebetween such that the first magnetic structure, the second magnetic structure, and the shaft are coaxially aligned.
 2. The fan assembly as claimed in claim 1, wherein the first magnetic structure and the second magnetic structure disposed opposite to each other in an axial direction.
 3. The fan assembly as claimed in claim 1, wherein the shaft directly contacts or magnetically attracts with the first magnetic structure or/and the second magnetic structure.
 4. The fan assembly as claimed in claim 1, further comprising at least one wear-resistant structure disposed between the shaft and the first magnetic structure, and the shaft and the second magnetic structure.
 5. The fan assembly as claimed in claim 4, wherein the shaft directly contacts the wear-resistant structure at a contact point.
 6. The fan assembly as claimed in claim 1, wherein a polarity of a side of the first magnetic structure facing the second magnetic structure is opposite to a polarity of a side of the second magnetic structure facing the first magnetic structure.
 7. The fan assembly as claimed in claim 1, wherein the rotor comprises at least one third magnetic structure with a first magnetic central plane, and the stator comprises at least one permeable structure with a second magnetic central plane corresponding to the third magnetic structure, wherein the first magnetic central plane is disposed slightly above or below the second magnetic central plane in an axial direction of the shaft.
 8. The fan assembly as claimed in claim 1, wherein the stator further comprises an opening defined at the center thereof with the shaft extended therein, and a protective structure disposed on a sidewall of the opening without contacting the shaft.
 9. The fan assembly as claimed in claim 8, wherein the protective structure is made of plastic, flexible material or vibration absorbing material.
 10. The fan assembly as claimed in claim 1, wherein an end surface of the shaft has a flat, curved, pointed, concave or convex shape, and the first magnetic structure and the second magnetic structure have end portions, each of the end portions, facing the shaft, with a curved, pointed, concave or convex shape corresponding to that of the end surface of the shaft.
 11. The fan assembly as claimed in claim 1, wherein when the shaft contacts the first and the second magnetic structures, the shape of the end surface of the shaft corresponds to the end portions of the first magnetic structure, the second magnetic structure or both.
 12. The fan assembly as claimed in claim 4, wherein an end surface of the shaft has a flat, curved, pointed, concave or convex shape, and the wear-resistant structure has an end, facing the shaft, with a flat, curved, pointed, concave or convex shape corresponding to that of the end surface of the shaft.
 13. The fan assembly as claimed in claim 4, wherein when the shaft contacts the wear-resistant structure at a contact point, the shape of the end surface of the shaft corresponds to the shape of the end of the wear-resistance.
 14. The fan assembly as claimed in claim 1, wherein the first or the second magnetic structures is a permanent magnet, a plastic magnet or an electromagnet.
 15. The fan assembly as claimed in claim 1, wherein the frame comprises an upper cover and a lower cover corresponding to each other and connected by fitting, engaging, gluing, locking or connecting via a cushion device.
 16. A fan assembly comprising: a base; a stator disposed on the base; a rotor coupled to the stator and having a shaft; a first magnetic structure disposed at a bottom of the base and positioned under the shaft to generate a magnetic interaction between the shaft and the first magnetic structure.
 17. The fan assembly as claimed in claim 16, further comprising a second magnetic structure disposed at a top of the base, and a third magnetic structure disposed inside a hub of the rotor to generate a magnetic interaction between the second and third magnetic structures.
 18. The fan assembly as claimed in claim 16, further comprising a protective structure disposed in an axial tube of the base and around the shaft.
 19. The fan assembly as claimed in claim 16, further comprising a wear-resistant structure disposed between an end of the shaft and the first magnetic structure.
 20. The fan assembly as claimed in claim 19, wherein the end of the shaft has a shape corresponding to that of the first magnetic structure or the wear-resistant structure so as to form a point contact therebetween. 